Novel terpyridine macrocyclic complexing agent and luminescence of its neutral Ln(III) complexes (Ln=Eu, Tb, Sm, Dy) in aqueous solution

A very convenient synthesis of an 18-membered triaza-macrocyclic ligand bearing one endocyclic terpyridine unit and three acetate pendant groups is reported. This nonadentate ligand forms very stable neutral lanthanide complexes in aqueous solution and efficiently shields the metal ion from the water environment. In this medium the Eu(III) and Tb(III) complexes are strongly fluorescent through an energy-transfer luminescence pathway (τ∼1 ms and Φ∼20%).